The present invention relates generally to the field of medical diagnostic systems, such as imaging systems. More particularly, the invention relates to a system and technique for generating images of a moving object.
In at least one known CT system configuration, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the xe2x80x9cimaging planexe2x80x9d. The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In at least one known type of imaging system, commonly known as a computer tomography (CT) system, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a xe2x80x9cviewxe2x80x9d. A xe2x80x9cscanxe2x80x9d of the object comprises a set of views made at different gantry angles during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object.
One method for reconstructing an image from a set of projection data is referred to in the art as the filtered backprojection technique. This process converts the attenuation measurements from a scan into integers called xe2x80x9cCT numbersxe2x80x9d or xe2x80x9cHounsfield unitsxe2x80x9d, which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
To reduce the total scan time required for multiple slices, a xe2x80x9chelicalxe2x80x9d scan may be performed. To perform a xe2x80x9chelicalxe2x80x9d scan, the patient is moved while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a one fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed. In addition to reduced scanning time, helical scanning provides other advantages such as improved image quality and better control of contrast.
In helical scanning, and as explained above, only one view of data is collected at each slice location. To reconstruct an image of a slice, the other view data for the slice is generated based on the data collected for other views. Helical reconstruction algorithms are known, and described, for example, in C. Crawford and K. King, xe2x80x9cComputed Tomography Scanning with Simultaneous Patient Translation,xe2x80x9d Med. Phys. 17(6), Nov/Dec 1990.
In order to generate images of a rapidly moving object, such as a heart, known imaging systems have minimized motion artifacts, caused by the movement of the heart, by utilizing a high rotational speed gantry or by incorporating electron beam technology. However, the high speed gantry system significantly increases the force applied to the x-ray source and the detector affecting performance of the system. The electron beam technology requires a very complex design that significantly increases the cost of the scanner. As a result, few systems are capable of generating images of a moving heart without generating images containing significant motion artifacts.
To generate images of a moving object, it is desirable to provide an imaging system which gathers segments of projection data of a selected phase of the object so that by combining the segments motion artifacts are minimized. It would also be desirable to provide such a system which generates a cross-sectional image of the entire object for a selected phase of the object.
Solutions to the problems described above have not heretofore included significant remote capabilities. In particular, communication networks, such as, the Internet or private networks, have not been used to provide remote services to such medical diagnostic systems. The advantages of remote services, such as, remote monitoring, remote system control, immediate file access from remote locations, remote file storage and archiving, remote resource pooling, remote recording, remote diagnostics, and remote high speed computations have not heretofore been employed to solve the problems discussed above.
Thus, there is a need for a medical diagnostic system which provides for the advantages of remote services and addresses the problems above. In particular, there is a need for remote upgrades, remote diagnostics, remote servicing, remote viewing, remote file storage, remote control, and remote adjustments to system parameters and functions. Furthermore, there is a need for contractual arrangements, such as, per use licenses which lease the medical diagnostic equipment based on use. Additionally, remote services may also include expert on-line assistance for image scanning techniques, image analysis, pathology detection, imaging unit maintenance, and other expert-aided operations.
One embodiment of the invention relates to a method for generating an image of an object using a computed tomography (CT) imaging system. The imaging system includes at least one x-ray detector array and at least one rotating x-ray source projecting an x-ray beam. The method includes the steps of identifying a physiological cycle of the object (the cycle including a plurality of phases); selecting at least one phase of the object; collecting at least one segment of projection data for each selected phase of the object during each rotation of each x-ray source; generating a projection data set by combining the projection data segments; and generating a cross-sectional image of the entire object from the projection data set.
Another embodiment of the invention relates to a computed tomography (CT) imaging system for generating an image of an object. The imaging system includes at least one x-ray detector array and at least one rotating x-ray source projecting an x-ray beam. The imaging system is configured to identify a physiological cycle of the object (the cycle including a plurality of phases); allow an operator to select at least one phase of the object; collect at least one segment of projection data for each selected phase of the object during each rotation of each said x-ray source; generating a projection data set by combining said projection data segments; and generate a cross-sectional image of the entire object from said projection data set.